a lot of deer have been taken with various 24 cailber rounds all thru the years, and no one can seriously argue the point. Now the OP wanted a low recoil round in what appears to be a Savage Mod. 10 series rifle. Short action, but also slightly longer than a Remington 700. It should take the 6.5x55 without too much trouble as it will handle the 57mm Mauser case as well. But will it handle the 55mm case with a 140 grain bullet? I just don't know, but of course he could simply drop down to a 120 grain bullet. Good round anyway. The 6.5x55 with factory loads is rather mild mannered, but is capable of much higher chamber pressure.

The surface area of the case head is the same for all the rounds mentioned sans a couple that are somewhat of an overkill. With similar chamber pressures ad similar bullet weights the rifle's recoil will be similar. (one of the laws of pneumatics). A 100 grain bullet in a .257 Roberts +P round at 3000 fps will be a shade under 51K. A 100 grain bullet in a .243 traveling at 3000 fps will generate about two percent more recoil due to chamber pressure alone 51,800 psi verses 50,800 psi). I doubt you'll see the difference in felt recoil. But you can gain another hundred fifty fps by using something like MAGPRO, and also increase the chamber pressure to 59.8K psi and about 20% more recoil.

Now compairing the 6mm Remington with a very stiff load to the .257 with a fairly stiff load and similar weight bullets we're going to see about 20% less felt recoil in the same rifle. Remember pressure is pressure no matter whatkind of a case your using, and the square inches of area with the chamber pressure pushing against it is what you will feel. I once had two rifles in 6mm, and the .257. Both were the same brand and had similar barrels and weight. The 6mm always had more recoil than the .257, and it was noticable enough that it even had slightly more recoil when I used the varmit barreled one off the same style action.
gary

He asked about a low recoil rifle for his Fiance and you are recommending a cartridge that uses 60+ gr of H1000 with a 140 gr bullet?

Obviously you did not read over the hole thread. They are not running the case at max pressure. Thats how they are getting low recol and over 3000 rounds out of a barrel. 130 vld's going 3250. You can't win the Hide cup if you can't spot your own hits out to 1100 yards. They have no kick.

+1 for the 243 Win. I've shot over 20 head of big game with mine using 100 gr Core Lokts and 100 gr Hornady BTSP without ever losing an animal. It's also accounted for 100+ coyotes and hundreds of rockchucks out to 750 yards. Better BC than the .25s, less recoil that most of the 6.5s, easy to find ammo and reloading components. IMO it's pretty hard to beat.